Current powder coating resins and formulations have one serious limitation: They generally need fairly high oven temperature (typically above 177° C. to have the good flow and cross-linking required for acceptable performance. Many of the substrates to be coated—such as plastics, wood and bio-composites—are quite temperature sensitive and cannot tolerate the high temperatures used in current powder coatings formulations. The use of such substrates has seen a significant increase in the last several years and is expected to grow quite dramatically in the future. See the Muthiah reference for an example of recent work in the area of low temperature cure powder coatings.
There is a need for a durable, cost-effective low temperature thermally cured powder coatings for temperature-sensitive substrates that also can be used on high temperature substrates such as metals. In such cases, lower temperature would lead to lower energy cost in the process. Lower costs should significantly increase the acceptance of the new technology.
There is a great deal of interest in the replacement of some petrochemical feedstocks with bio-based feedstocks for use in a wide range of application areas. Evidence of this interest is reflected in the number of review articles that have been published through the years. Efforts to utilize bio-based feedstock in the synthesis of polyester resins is exemplified in U.S. Pat. No. 6,063,464 and in the paper by Guo, et. al. (see below), wherein corn bio-mass derived isosorbide is used in the synthesis of polyester materials.
There is also a need to produce powder coatings that flow-out and cure at lower temperatures than those currently used in the industry. Powder coatings offer environmental advantages in that they are very low in in-use emissions of VOCs. Unfortunately, some of that advantage is lost due to high energy demands in the cure cycle and the rough finishes typically derived from them owing to poor flow-out at low temperatures.
Other related patents and journal articles include;    LOW TEMPERATURE CURE: U.S. Pat. No. 6,703,070 March 2004 Muthiah    SYNTHESIS AND PROCESSING: EP1491593 December 2004 Mons    BIO-BASED MATERIALS REVIEWS: Applied Microbiology and Biotechnology (2001), 55(4), 387-394. Huttermann, A.; Mai, C.; Kharazipour, A. “Modification of lignin for the production of new compounded materials”;    Biopolymers from Renewable Resources (1998), 1-29. Kaplan, David L. “Introduction to biopolymers from renewable resources”;    Bioresource Technology (1994), 49(1), 1-6. Sharma, D. K.; Tiwari, M.; Behera, B. K. “Review of integrated processes to get value-added chemicals and fuels from petrocrops”; and    Applied Biochemistry and Biotechnology (1988), 17 7-22. Narayan, Ramani. “Preparation of bio-based polymers for materials applications”.    BIO-BASED RESIN SYNTHESIS: Abstracts of Papers, 224th ACS National Meeting, Boston, Mass., United States, Aug. 18-22, 2002 (2002). Guo, Yinzhong; Mannari, Vijaykumar M.; Massingill, John L., Jr. “Hyperbranched bio-based polyols”.    POWDER COATINGS: “Powder Coatings Volume 1: The Technology, Formulation, and Application of Powder Coatings”. Howell, David M. John Wiley and Sons, London, 2000.    Polymer Preprints 2003, 44(1). Gedan-Smolka, Michaela; Lehmann, Dieter; Lehmann, Frank. “Catalysis in Uretdione Powder Coatings Enables Innovative Processing Lines”.
In addition to the need for low temperature flow and cure in powder coatings, there is also a need for good dispersion of pigments within a coating matrix, regardless of the coating type. To accomplish this, polymers are designed that have components with differing compatibilities. Polymeric dispersants stabilize pigments and other ingredients in paints, coatings, and ink systems via, most typically, steric stabilization. Polymeric dispersants have a two-component structure comprised of anchoring groups and polymeric chains. Most typically the anchoring groups are polar materials that interact with the is particle surfaces and the polymeric chains which are compatible with the continuous phase of the coating. In effect, the polymeric groups form a coating around the particles, preventing them from making contact and agglomerating into larger, incompatible aggregates.
There are many anchoring group/polymer configurations that might be expected to give effective polymeric dispersants. The inventive resin has polar carboxylic anchoring sites and non-polar vegetable oil chains and can therefore act as a dispersant as well as a binder. A curing binder that can also act as a dispersant could eliminate the need for separate additives for dispersing many pigments. Related art includes U.S. Pat. No. 5,959,066; U.S. Pat. No. 6,025,061; U.S. Pat. No. 6,063,464; and U.S. Pat. No. 6,107,447.